The present invention relates to a system for transmitting high definition television pictures over a channel having a comparatively narrow passband, the system comprising on the one hand a transmitting section provided with a picture pick-up member for supplying samples defining the elements forming said pictures, these elements being in positions which are distributed over the pictures along lines of different parities, a filter member for filtering said samples, a sub-sampling member for taking certain samples from the output of the filter member and a transmission circuit for transmitting the samples taken over the channel in accordance with four transmission fields, and on the other hand at least one receiving section comprising a receiving circuit for receiving the samples coming from the transmitter circuit. The present invention also relates to a receiver and a transmitter suitable for the system.
Systems of this type are well known and can find important uses more specifically in the transmission of high definition pictures which are compatible with the "MAC" standards and more in particular for the "D2-MAC" standard (recommendation 601 of the C.C.I.R ).
A known system of this type is disclosed in the article "A Single Channel HDTV Broadcast System--The MUSE--" by Yuichi Ninomiya et al., published in the periodical "NHK Laboratories Note", serial number 304, September 1984. This MUSE system which is not adapted to said standards can be done so easily by linearly modifying its different characteristic parameters. The known system utilizes, for the transmission of the samples of a picture, a sampling structure which extends over four fields. Elements belonging to different spatial positions are transmitted in these four consecutive fields.
Although these systems are designed for transmitting high definition Pictures, they must also be compatible for the reception of these images by a receiver adapted to the normal definition. The normal reception in accordance with the standard D2-MAC/packet then provides a picture with a lower definition.